Portable Weather Information Display System (PWIDS)
by
Donald P. Storwold Jr., Scott F. Halvorson, John M. White, Robert D. Feldman
Meteorology & Obscurants Division
U.S. Army Dugway Proving Ground
Dugway, Utah; USA 84022-5000
TEL: (435) 831-5101
FAX: (435) 831-5289
storwold@dpg.army.mil
Introduction
The Portable Weather Information Display System (PWIDS) is a lightweight
mobile surface atmospheric measurement station, which was developed to support
field tests at the U.S. Army’s Dugway Proving Ground (DPG). PWIDS is a hardware/software system that collects, processes, and displays meteorological parameters from an array of remote, portable sensing stations. It’s primary function is to
provide test directors with real-time meteorological observations to assist in their
“go/no-go” test decisions and in post-test forensic analyses of test results. PWIDS
has also been used in climatological studies where real-time data collection was not
critical.
In its most common configuration, PWIDS collects wind speed, wind direction,
temperature, and relative humidity measurements at 1-s intervals. It then averages
these data over a 10-s period and outputs the averages to a data collection computer
via a spread-spectrum radio link. Up to 40 PWIDS stations can be deployed over an
area in excess of 1000 km2. PWIDS is highly configurable and utilizes solar power
and radio frequency communication, which eliminate the need for any hardwired
connections. Although measurements can be made at various heights, the sensors
are normally mounted at the top of a 2-m mast. Because of the adaptive nature of
PWIDS software, data collection and averaging rates can be modified to fit specific
needs.
Hardware
The PWIDS hardware configuration was designed by the Dugway Meteorology
Division. Most of the hardware comprising PWIDS is manufactured by Campbell
Scientific, Inc. in Logan, Utah. This hardware consists of a CR10, 21X, or 23X datalogger; SC32A interface; PS12LA power supply/regulator; CS500 temperature/ rel-
ative humidity probe; CM10 tripod; and ENC 12/14 enclosure. Figure-1 illustrates a
typical PWIDS installation.
The wind sensing is accomplished using an R.M. Young 05103 wind monitor
or an R.M. Young 81000 sonic anemometer. A FreeWave spread spectrum radio
operating at 902 – 928 MHz provides the communications link. For long-term climatological studies, an SM16M storage module manufactured by Campbell Scientific,
Inc. normally is utilized in place of the radio link.
Several PWIDS programs were written to control the CR10, 21X, or 23X dataloggers. These programs configure the output stream, sample rates, and averaging
and output rates. The programs also activate installed sensors and convert collected
data to desired units of measure. The variation in hardware configuration determines
which program is loaded into the datalogger.
PWIDS is highly adaptable. The meteorological sensors can be mounted on
tripods or towers; sampling and output rates can range from 10 Hz to several
minutes; data collection can be accomplished via radio link, direct connection, or
storage module; and wind sensor configuration can vary from mechanical wind sensor to sonic anemometers. The hardware configurations are predetermined based
on requirements or results desired. Figure-2 shows a modified PWIDS configuration
on a traffic light/street light pole in an urban area.
Figure 1 – Normal Installation
Figure 2 – Modified Installation
Software
The PWIDS software also was developed by the Dugway Meteorology Division. This software consists of an ingest program, display program, and data manipulation utilities. Both the ingest and display programs are written under a Microsoft
Windows platform in the Practical Export and Report Language (PERL), which enables their use under a variety of operating systems (e.g. – Linux, Unix, etc.) with only
minor alteration.
The PWIDS ingest program: 1) reads incoming data, 2) averages high frequency observations as specified by the user, and 3) archives the averaged data.
Whether the PWIDS is hardwired or radioed, the application continuously reads
ASCII data that are sent via the serial port from the PWIDS station. All incoming data
are saved in a flat file, and these data are averaged to 1-min increments for display
purposes. The averaged data also are archived into a local database, which is generally used for input to a dispersion model. The flat files can be shared across a network for input into multiple PWIDS displays.
The PWIDS display is a Graphical User Interface (GUI) that can provide a variety of displays. The observed 1-min averaged wind vectors are plotted at each
PWIDS site on an area map, allowing users to look at 2-D wind fields in real time.
The user can choose to display a numeric table of current weather conditions (e.g. –
wind, temperature, relative humidity, etc.). A table of statistical PWIDS data for the
last 30-min can also be displayed at the user’s request. All displays are synchronized to maintain continuity between the forecast office and the field displays. Figure-3 illustrates a typical PWIDS display.
Vapor/aerosol cloud trajectory algorithms are available in the PWIDS software
and can be used to display historical or real-time trajectories. The trajectory calculations use the momentum equation to advect the air parcel. No terrain effects are included in the trajectory calculations other than those implicit in the 2-m wind measurements. The historical trajectory is a plotted line of surface parcel path from a position defined by the user using historical PWIDS data. The user defines the location
by moving the cursor to a point on the map and then clicking the mouse button. The
cursor over the map displays high- resolution geographic information in both terrestrial and Universal Transverse Mercator (UTM) coordinates. The user determines the
time length of the trajectory. The real-time trajectory is similar to the historical trajectory, but the parcel trajectory is only updated by real-time data. Up to 10 trajectories
can be displayed simultaneously. Multiple trajectories allow the user to simulate a
line source. The user can also display a table of each parcel’s location and wind information along its computed trajectory. Questionable wind observations can be
flagged by the user and not used in any of the trajectory calculations.
Figure 3 – Typical PWIDS Display Screen
PWIDS data must be manipulated upon completion of a test program to make
the data usable for historical purposes. As noted above, a large flat ASCII file is created during the data collection process, with data from all PWIDS stations placed in
one common file. This file must be divided into individual station files, subjected to
quality control, processed, and archived. Again, the Meteorology Division at Dugway
has written several utility programs to handle this data manipulation.
Summary
One of the unique features of PWIDS is the fast data retrieval process that is
inherent with the system. While most meteorological data collection platforms poll
remote stations for data, PWIDS allows individual stations to transmit their data at
predetermined intervals. The lack of “communication handshaking” allows larger volumes of data at much faster rates.
PWIDS has become an integral part of the test mission at the Dugway Proving
Ground. Often, 50 of these stations are simultaneously collecting data for several
test programs. Their proven reliability provides meteorologists and modelers with real-time data for quick and accurate forecasting.